For many conditions, injection of indicated medication can occur at home. Many patients, however, are needle-averse or suffer from needle-phobia, and/or have other difficulties including inability or lack of desire to follow complex instructions, fear of self administration, and danger of needle stick injury and cross contamination. Ensuring treatment compliance can be problematic. In addition, it is a problem that patients may need to be trained to self administer an injection, although for some indications the number of injections they would self administer is only a few. In addition, a needle and syringe in general needs to be filled, and for some formulations the drug is dried and requires reconstitution, which further complicates self administration and reduces compliance. These issues often rule out the possibility of treatment in a home setting, either self treatment or by a relatively un-trained care giver such as a family member. The inability to dose at home can lead to higher costs of therapy, delay in treatment, reduced compliance, reduced comfort, and potential exposure to hospital acquired infections.
Some issues are particularly acute in the context of elevated viscosity formulations, including but not limited to controlled release formulations, and formulations of biologic drugs, such as Monoclonal Antibodies (MABs). Elevated viscosity leads to many delivery difficulties, such as high required hand strength for a needle and syringe, long delivery times, and additional pain and fear associated with a large bore needle. Thus there is a need to deliver these compounds without a needle, preferably in a rapid, automated fashion using a system that does not require filling, reconstitution, or other complex procedures.
A dosage form that is easy and fast to self administer can be crucial for acute, debilitating conditions, for example small molecules such at triptans for migraine and cluster headache, or glucagon, a polypeptide for the acute treatment of hypoglycemia. Oral drugs have the advantage that they are easy to self administer. However, many drugs, especially peptide and protein drugs have very limited oral bioavailability, due to digestion and first pass liver metabolism. Additionally, absorption following oral delivery is delayed, with time to peak plasma concentrations (Tmax) of ˜40 minutes or longer.
It is known that needle free injectors can address the issues above of patient needle-phobia, compliance with therapy, needle stick injury, and cross contamination. However, it is important that the design parameters, such as the pressure in the drug container, the size of the injection orifice or orifi, and the pressure profile during delivery, be properly chosen to ensure successful injection. Improper choice of parameters can lead to problems such as wet (incomplete) injection, or at the other extreme too deep, for example intra-muscular, injection.
Needle-free injectors are available using many different types of energy sources, and the energy may be supplied by the user, for example where a spring is manually compressed and latched to temporarily store the energy until it is required to actuate the injector. Alternatively, the injector may be supplied having the energy already stored—for instance by means of a pre-compressed spring (mechanical or compressed gas), or by pyrotechnic charge.
Some injectors are intended for disposal after a single use, whereas others have a re-loadable and/or multi-dose energy storage means and a single or multi-dose medicament cartridge, and there are many combinations to suit particular applications and markets. For the purposes of the present disclosure, the term “actuator” will be used to describe the energy storage and release mechanism, whether or not it is combined with a medicament cartridge. In all cases, it is necessary to arrange for sufficient force at the end of the delivery to deliver the entire dose of medicament at the required pressure.
EP 0 063 341 and EP 0 063 342 disclose a needle-free injector which includes a piston pump for expelling the liquid to be injected, which is driven by a motor by means of a pressure agent. The liquid container is mounted laterally to the piston pump. The amount of liquid required for an injection is sucked into the pump chamber by way of an inlet passage and a flap check valve when the piston is retracted. As soon as the piston is moved in the direction of the nozzle body the liquid is urged through the outlet passage to the nozzle and expelled. The piston of the piston pump is a solid round piston.
EP 0 133 471 describes a needle-free vaccination unit which is operated with carbon dioxide under pressure, from a siphon cartridge by way of a special valve.
EP 0 347 190 discloses a vacuum compressed gas injector in which the depth of penetration of the injected drug can be adjusted by means of the gas pressure and the volume of the drug can be adjusted by way of the piston stroke.
EP 0 427 457 discloses a needle-free hypodermic syringe which is operated by means of compressed gas by way of a two-stage valve. The injection agent is disposed in an ampoule which is fitted into a protective casing secured to the injector housing. The ampoule is fitted on to the end of the piston rod. Disposed at the other end of the ampoule is the nozzle whose diameter decreases towards the end of the ampoule.
WO 89/08469 discloses a needle-free injector for one-time use. WO 92/08508 sets forth a needle-free injector which is designed for three injections. The ampoule containing the drug is screwed into one end of the drive unit, with the piston rod being fitted into the open end of the ampoule. At its one end, the ampoule contains the nozzle through which the drug is expelled. A displaceable closure plug is provided approximately at the center of the length of the ampoule. The dose to be injected can be adjusted by changing the depth of the ampoule. The piston rod which projects from the drive unit after actuation of the injector is pushed back by hand. Both units are operated with compressed gas.
WO 93/03779 discloses a needle-free injector with a two-part housing and a liquid container which is fitted laterally to the unit. The drive spring for the piston is stressed by means of a drive motor. The spring is released as soon as the two parts of the housing are displaced relative to each other by pressing the nozzle against the injection location. Respective valves are provided in the intake passage for the liquid and in the outlet of the metering chamber.
WO 95/03844 discloses a further needle-free injector. It includes a liquid-filled cartridge which at one end includes a nozzle through which the liquid is expelled. At the other end the cartridge is closed by a cap-type piston which can be pushed into the cartridge. A piston which is loaded by a pre-stressed spring, after release of the spring, displaces the cap-type piston into the cartridge by a predetermined distance, with the amount of liquid to be injected being expelled in that case. The spring is triggered as soon as the nozzle is pressed sufficiently firmly against the injection location. This injector is intended for one-time or repeated use. The cartridge is arranged in front of the spring-loaded piston and is a fixed component of the injector. The position of the piston of the injector which is intended for a plurality of uses is displaced after each use by a distance in a direction towards the nozzle. The piston and the drive spring cannot be reset. The pre stressing of the spring is initially sufficiently great to expel the entire amount of liquid in the cartridge all at once. The spring can only be stressed again if the injector is dismantled and the drive portion of the injector assembled with a fresh, completely filled cartridge.
U.S. Pat. No. 5,891,086 describes a needle-free injector, combining an actuator and a medicament cartridge. The cartridge is pre-filled with a liquid to be injected in a subject, and having a liquid outlet and a free piston in contact with the liquid, the actuator comprising an impact member urged by a spring and temporarily restrained by a latch means, the impact member being movable in a first direction under the force of the spring to first strike the free piston and then to continue to move the piston in the first direction to expel a dose of liquid through the liquid outlet, the spring providing a built-in energy store and being adapted to move from a higher energy state to a lower energy state, but not vice versa. The actuator may comprise trigger means to operate the said latch, and thus initiate the injection, only when a predetermined contact force is achieved between the liquid outlet of the said cartridge and the subject.
In U.S. Pat. No. 3,859,996, Mizzy discloses a controlled leak method to ensure that the injector orifice is placed correctly at the required pressure on the subject's skin at the correct normal to the skin attitude. When placement conditions are met, controlled leak is sealed off by contact pressure on the subject's skin, the pressure within the injector control circuit rises until a pressure sensitive pilot valve opens to admit high pressure gas to drive the piston and inject the medicament.
In WO Patent 82/02835, Cohen and Ep-A-347190 Finger, disclose a method to improve the seal between the orifice and the skin and prevent relative movement between each. This method is to employ a vacuum device to suck the epidermis directly and firmly onto the discharge orifice. The discharge orifice is positioned normal to the skin surface in order to suck the epidermis into the orifice. This method for injection of the medicament into the skin and the injector mechanism are different and do not apply to the present invention because of its unique ampoule design.
In U.S. Pat. No. 3,859,996 Mizzy discloses a pressure sensitive sleeve on the injector which is placed on the subject, whereby operation of the injector is prevented from operating until the correct contact pressure between orifice and the skin is achieved. The basic aim is to stretch the epidermis over the discharge orifice and apply the pressurized medicament at a rate which is higher than the epidermis will deform away from the orifice.
In U.S. Pat. No. 5,480,381, T. Weston discloses a means of pressuring the medicament at a sufficiently high rate to pierce the epidermis before it has time to deform away from the orifice. In addition, the device directly senses that the pressure of the discharge orifice on the subject's epidermis is at a predetermined value to permit operation of the injector. The device is based on a cam and cam follower mechanism for mechanical sequencing, and contains a chamber provided with a liquid outlet for expelling the liquid, and an impact member, to expel the liquid.
In U.S. Pat. No. 5,891,086, T. Weston describes a needle-free injector that contains a chamber that is pre-filled with a pressurized gas which exerts a constant force on an impact member in order to strike components of a cartridge and expulse a dose of medicament. This device contains an adjustment knob which sets the dose and the impact gap, and uses direct contact pressure sensing to initiate the injection. Further examples and improvements to this needle-free injector are found in U.S. Pat. No. 6,620,135, U.S. Pat. No. 6,554,818, U.S. Pat. No. 6,415,631, U.S. Pat. No. 6,409,032, U.S. Pat. No. 6,280,410, U.S. Pat. No. 6,258,059, U.S. Pat. No. 6,251,091, U.S. Pat. No. 6,216,493, U.S. Pat. No. 6,179,583, U.S. Pat. No. 6,174,304, U.S. Pat. No. 6,149,625, U.S. Pat. No. 6,135,979, U.S. Pat. No. 5,957,886, U.S. Pat. No. 5,891,086, and U.S. Pat. No. 5,480,381, incorporated herein by reference.
A number of biologically-active agents in viscous formulations would benefit from being delivered using the needle-free injector. This group could consist of (but not limited to) anti-inflammatory agents, antibacterial agents, antiparasitic agents, antifungal agents, antiviral agents, anti-neoplastic agents, analgesic agents including opioids, drugs for the treatment of arthritis including rheumatoid arthritis, antibodies, including monoclonal antibodies, protein and peptide drugs, including recombinant proteins and peptides, antipsychotics, anesthetics, vaccines, central nervous system agents, growth factors, hormones, antihistamines, osteoinductive agents, cardiovascular agents, anti-ulcer agents, bronchodilators, vasodilators, birth control agents and fertility enhancing agents, interferon alpha, growth hormone, osteoporosis drugs including PTH and PTH analogs and fragments, obesity drugs, psychiatric drugs, anti-diabetes, female infertility, AIDS, treatment of growth retardation in children, hepatitis, multiple sclerosis, migraine headaches, and allergic reactions.